Today, full-system encryption in software is both feasible and practical -- although how practical will depend on the workload involved. But it's not a security silver bullet, much as it might seem to be from the outside. It can, and does, add a layer of protection that greatly reduces the risk of data compromise in the event hardware is lost or stolen. But that protection depends entirely on how it's implemented, and whether or not the user's been educated in the way an encrypted system works.